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Control of microtubule nucleating activity in the cytoplasm of maturing mouse oocytes
A Van Cauwenberge1, H Alexandre
1Laboratory of Molecular Cytology and Embryology, Faculty of Sciences, Free University of Brussels, Belgium.
Abstract:
Taxol, a drug which promotes microtubule assembly, was used to assess the microtubule nucleating activity of pericentriolar material (PCM) in mouse oocytes prevented from undergoing germinal vesicle breakdown (GVBD), compared with oocytes allowed to proceed normally through GVBD and also in nucleate and anucleate oocyte fragments. Both immunofluorescence staining and ultrastructural analysis reveal that taxol induces aster formation in the cortex of oocytes undergoing GVBD, while formation of a continuous sheet of microtubule bundles parallel to the membrane is induced in metabolically GV-arrested oocytes. Since taxol also induces the formation of asters in anucleate as well as in nucleate oocyte fragments, provided they are not treated with activators of protein kinases A or C, it is concluded that microtubule nucleating activity is related to the acquisition of Maturation Promoting Factor (MPF) and does not require mixing between the nucleoplasm and cytoplasm.
Insights
Mouse oocyte maturation involves microtubule assembly, influenced by pericentriolar material (PCM). Taxol treatment revealed that microtubule nucleation depends on Maturation Promoting Factor (MPF) acquisition, not nucleoplasm-cytoplasm mixing.
Area of Science:
- Cell Biology
- Developmental Biology
- Molecular Biology
Background:
- Microtubules are crucial for cell division and organization.
- Pericentriolar material (PCM) is a key microtubule-nucleating structure.
- Oocyte maturation involves complex cellular events, including microtubule dynamics.
Purpose of the Study:
- To investigate the microtubule nucleating activity of PCM in mouse oocytes.
- To determine the role of oocyte maturation status and MPF in microtubule nucleation.
- To assess whether nucleoplasm-cytoplasm interaction is necessary for microtubule nucleation.
Main Methods:
- Treatment of mouse oocytes with Taxol, a microtubule-promoting agent.
- Comparison of microtubule organization in oocytes undergoing germinal vesicle breakdown (GVBD) versus those arrested.
- Analysis of microtubule formation in nucleate and anucleate oocyte fragments.
- Immunofluorescence staining and ultrastructural analysis.
Main Results:
- Taxol induced aster formation in the cortex of oocytes undergoing GVBD.
- A continuous sheet of microtubule bundles formed in metabolically GV-arrested oocytes.
- Taxol induced aster formation in both nucleate and anucleate oocyte fragments (without kinase activators).
Conclusions:
- Microtubule nucleating activity in oocytes is linked to the acquisition of Maturation Promoting Factor (MPF).
- Microtubule nucleation does not require mixing between the nucleoplasm and cytoplasm.
- PCM's nucleating capacity is regulated by the oocyte's maturation state.